Buggy code:
public abstract class VersionedExtensionCommon implements Extension { public static final String SUBSYSTEM_NAME = "test-subsystem" ; public static final String EXTENSION_NAME = "org.jboss.as.test.transformers" ; static final PathElement SUBSYSTEM_PATH = PathElement . pathElement ( SUBSYSTEM , VersionedExtensionCommon . SUBSYSTEM_NAME ) ; static final AttributeDefinition TEST_ATTRIBUTE = SimpleAttributeDefinitionBuilder . create ( "test-attribute" , STRING ) . build ( ) ; private VersionedExtensionCommon . SubsystemParser parser = new VersionedExtensionCommon . SubsystemParser ( VersionedExtensionCommon . EXTENSION_NAME ) ; public VersionedExtensionCommon . SubsystemParser getParser ( ) { } protected ManagementResourceRegistration initializeSubsystem ( final SubsystemRegistration registration ) { registration . registerXMLElementWriter ( getParser ( ) ) ; final ManagementResourceRegistration reg = registration . registerSubsystemModel ( new VersionedExtensionCommon . TestResourceDefinition ( VersionedExtensionCommon . SUBSYSTEM_PATH , new VersionedExtensionCommon . TestModelOnlyAddHandler ( VersionedExtensionCommon . TEST_ATTRIBUTE ) ) { @ Override public void registerAttributes ( ManagementResourceRegistration resourceRegistration ) { resourceRegistration . registerReadWriteAttribute ( VersionedExtensionCommon . TEST_ATTRIBUTE , null , new VersionedExtensionCommon . BasicAttributeWriteHandler ( VersionedExtensionCommon . TEST_ATTRIBUTE ) ) ; } } ) ; <START_BUG> reg . registerOperationHandler ( DESCRIBE , INSTANCE , INSTANCE , false , PRIVATE ) ; <END_BUG> return reg ; } @ Override public void initializeParsers ( ExtensionParsingContext context ) { } protected ModelNode createAddOperation ( PathAddress addr ) { } protected abstract void addChildElements ( List < ModelNode > list ) { } protected static class TestResourceDefinition extends SimpleResourceDefinition { protected TestResourceDefinition ( PathElement element ) { } protected TestResourceDefinition ( PathElement element , OperationStepHandler addHandler ) { } } private static class TestModelOnlyAddHandler extends AbstractAddStepHandler { AttributeDefinition [ ] attributes ; public TestModelOnlyAddHandler ( AttributeDefinition ... attributes ) { } @ Override protected void populateModel ( final ModelNode operation , final ModelNode model ) throws OperationFailedException { } } private static OperationStepHandler NOOP_REMOVE_HANDLER = new AbstractRemoveStepHandler ( ) { @ Override protected void performRuntime ( OperationContext context , ModelNode operation , ModelNode model ) throws OperationFailedException { } } ; private static class BasicAttributeWriteHandler extends AbstractWriteAttributeHandler < Void > { protected BasicAttributeWriteHandler ( AttributeDefinition def ) { } @ Override protected boolean applyUpdateToRuntime ( OperationContext context , ModelNode operation , String attributeName , ModelNode resolvedValue , ModelNode currentValue , HandbackHolder < Void > voidHandbackHolder ) throws OperationFailedException { } @ Override protected void revertUpdateToRuntime ( OperationContext context , ModelNode operation , String attributeName , ModelNode valueToRestore , ModelNode valueToRevert , Void handback ) throws OperationFailedException { } } private class SubsystemParser implements XMLElementReader < List < ModelNode > > , XMLElementWriter < SubsystemMarshallingContext > { private final String namespace ; private SubsystemParser ( String namespace ) { } @ Override public void readElement ( XMLExtendedStreamReader reader , List < ModelNode > list ) throws XMLStreamException { } @ Override public void writeContent ( XMLExtendedStreamWriter streamWriter , SubsystemMarshallingContext context ) throws XMLStreamException { } } static ResourceDescriptionResolver TEST_RESOURCE_DESCRIPTION_RESOLVER = new NonResolvingResourceDescriptionResolver ( ) ; }

Fix:
reg . registerOperationHandler ( DEFINITION , INSTANCE ) ;